chapter 1 earth science etextbook

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Chapter 1

What is Earth Science?

1.1 Nature of Science

Lesson Objectives

Explain the importance of asking questions. State the steps of the scientific method. Describe the three major types of scientific models. Use appropriate safety precautions inside and outside the science laboratory.

Introduction

Think of your favorite science fiction movie. What is it about? Maybe its about spaceships going to distantplanets, or people being cloned in laboratories, or undersea civilizations, or robots that walk among us.These entertaining imaginings are make-believe fantasies, thats why theyre called science fiction. Theyare not real. But why are they called science fiction?

The answer is that science uses a disciplined process to answer questions. In science, disciplined does notmean well-behaved. It means following orderly steps in order to come up with the best answers. Scienceinvolves observing, wondering, categorizing, communicating, calculating, analyzing, and much more. Inorder to convert creativity into reality, we need science. In order to travel beyond where anyone has gonebefore, we need science. In order to understand the world, make sense of it, and conserve it, we needscience. In order to confirm our best guesses about the universe and the things in it, we need science.Science fiction stories extend and expand on all the ideas of science and technology in creative ways.

Asking Questions

Why is the sky blue?

How tall will this tree grow?

Why does the wind blow so hard?

Will it be cold tonight?

How many stars are out there?

Are there planets like Earth that orbit about some of those stars?

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How did this rock get holes in it?

Why are some rocks sharp and jagged, while others are round?

You probably ask yourself a thousand questions a day, many of which you never ask anyone else. For manyof the questions you do ask, you never even get an answer. But your brain keeps churning with questionsand curiosity. We cant help but want to know.

The list of questions above are some of the same questions that scientists ask. Science has developed overcenturies and centuries, and our ability to measure the tiniest trait has increased immensely. So althoughthere is no wrong question, there are questions that lend themselves more to the scientific process thanothers. In other words, some questions can be investigated using the scientific method while others rely onpure faith or opinion.

Scientific Methods

The scientific method is not a list of instructions but a series of steps that help to investigate a question. Byusing the scientific method, we can have greater confidence in how we evaluate that question. Sometimes,the order of the steps in the scientific method can change, because more questions arise from observationsor data that we collect. The basic sequence followed in the scientific method is illustrated in Figure 1.1.

Question

The scientific method almost always begins with a question that helps to focus the investigation. Whatare we studying? What do we want to know? What is the problem we want to solve? The best questionsfor scientific investigation are specific as opposed to general, they imply what factors may be observed ormanipulated.

Example:A farmer has heard of a farming method called no-till farming. In this method, certaintechniques in planting and fertilizing eliminate the need for tilling (or plowing) the land. Will no-till

farming reduce the erosion of the farmland (Figure 1.2)?

Research

Before we go any further, it is important to find out what is already known about the topic. You canresearch a topic by looking up books and magazines in the library, searching on the Internet, and eventalking to people who are experts in the area. By learning about your topic, youll be able to makethoughtful predictions. Your experimental design might be influenced by what you have researched. Oryou might even find that your question has been researched thoroughly. Although repeating experimentsis valid and important in science, you may choose to introduce new ideas into your investigation, or youmay change your initial question.

Example: The farmer decides to research the topic of no-till farming (Figure 1.3). She finds sources onthe Internet, at the library, and at the local farming supply store that discuss what type of fertilizer mightbe used and what the best spacing for her crop would be. She even finds out that no-till farming canbe a way to reduce carbon dioxide emissions into the atmosphere, which helps in the fight against globalwarming.

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Figure 1.1: The Scientific Method.

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Figure 1.2: Soil Erosion

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Figure 1.3: The farmer would need to research no-till farming methods.

Hypothesis

Now that you have researched the topic, you can make an educated guess or explanation to the question.This is your hypothesis. The best hypothesis is directly related to the question and is testable, so thatyou can do experiments to determine whether your hypothesis is correct.

Example: The farmer has researched her question and developed the following hypothesis:

No-till farming will decrease the soil loss on hills of similar steepness as compared to the traditional farmingtechnique because there will be less disturbance to the soil.

A hypothesis can be either proved or disproved by testing. If a hypothesis is repeatedly tested and provento be true, then scientists will no longer call it a hypothesis.

Experiment

Not all questions can be tested by experimentation. However, many questions present us with ways to testthem that give us the clearest conclusions. When we design experiments, we select the factor that will bemanipulated or changed. This is the independent variable. We will also choose all of the factors thatmust remain the same. These are the experimental controls. Finally, we will choose the factor that weare measuring, as we change the independent variable. This is the dependent variable. We might saythat the dependent variable depends on the independent variable. How much soil is eroded depends onthe type of farming technique that we choose.

Example: The farmer will conduct an experiment on two separate hills with similar slopes or steepnesses(Figure 1.4). On one hill, he will use a traditional farming technique which includes plowing to stir upthe nutrients in the soil. On the other hill, he will use a no-till technique by spacing plants further apartand using specialized equipment that plants the plants without tilling. He will give both sets of plantsidentical amounts of water and fertilizer.

In this case, the independent variable is the farming techniqueeither traditional or no-tillbecause thatis what is being manipulated. In order to be able to compare the two hills, they must have the same slopeand the same amount of fertilizer and water. If one had a different slope, then it could be the angle thataffects the erosion, not the farming technique, for example. These are the controls. Finally, the dependentvariable is the amount of erosion because the farmer will measure the erosion to analyze its relatedness to

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Figure 1.4: A farmer takes careful measurements in the field.

the farming technique.

Data and Experimental Error

Data can be collected in many different ways depending on what we are interested in finding out. Scientistsuse electron microscopes to explore the universe of tiny objects and telescopes to venture into the universeitself. Scientists routinely travel to the bottom of the ocean in research submersibles to make observationsand collect samples. Probes are used to make observations in places that are too dangerous or too imprac-tical for scientists to venture. Probes have explored the Titanic as it lay on the bottom of the ocean andto other planets in our solar system. Data from the probes travels through cables or through space to acomputer where it can be manipulated by scientists. Of course, many scientists work in a laboratory andperform experiments and analyses on a bench top.

During an experiment, we may make many measurements. These measurements are our observationsthat will be carefully recorded in an organized manner. This data is often computerized and kept in aspreadsheet that can be in the form of charts or tables that are clearly labeled, so that we wont forgetwhat each number represents. Data refers to the list of measurements that we have collected. We maymake written descriptions of our observations but often, the most useful data is numerical. Even data thatis difficult to measure with a number is sometimes represented numerically. For example, we may makeobservations about cleanliness on a scale from one to ten, where ten is very clean and one is very dirty.Statistical analyses also allow us to make more effective use of the data by allowing us to show relationshipsbetween different categories of data. Statistics can make sense of the variability (spread) in a data set. Bygraphing data, we can visually understand the relationships between data. Besides graphs, data can bedisplayed as charts or drawings so that other people who are interested can see the relationships easily.

As in just about every human endeavor, errors are unavoidable. In an experiment, systematic errors areinherent in the experimental setup so that the numbers are always skewed in one direction or another. Forexample, a scale may always measure one-half ounce high. Like many systematic errors, the scale can berecalibrated or the error can be easily corrected. Random errors occur because no measurement can bemade exactly precisely. For example, a stopwatch may be stopped too soon or too late. This type of erroris reduced if many measurements are taken and then averaged. Sometimes a result is inconsistent with theresults from other samples. If enough tests have been done, the inconsistent data point can be thrown outsince likely a mistake was made in that experiment. The remaining results can be averaged.

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Not all data is quantified, however. Our written descriptions are qualitative data, data that describes thesituation observed. In any case, data is used to help us draw logical conclusions.

Conclusions

After you have summarized the results of the experiments and presented the data as graphs, tables anddiagrams, you can try to draw a conclusion from the experiments. You must gather all your evidence and

background information. Then using logic you need to try formulate an explanation for your data. What isthe answer to the question based on the results of the experiment? A conclusion should include commentsabout the hypothesis. Was the hypothesis supported or not? Some experiments have clear, undeniableresults that completely support the hypothesis. Others do not support the hypothesis. However, allexperiments contribute to our wealth of knowledge. Even experiments that do not support the hypothesismay teach us new information that we can learn from. In the world of science, hypotheses are rarely provedto one hundred percent certainty. More often than not, experiments lead to even more questions and morepossible ways of considering the same idea.

Example: After a full year of running her experiment, the farmer finds 2.2 times as much erosion on thetraditionally farmed hill as on the no-till hill. She intends to use no-till methods of farming from now onand to continue researching other factors that may affect erosion. The farmer also notices that plants in

the no-till plots are taller and the soil moisture seems higher. She decides to repeat the experiment andmeasure soil moisture, plant growth, and total water needed to irrigate in each kind of farming.

Theory

If a topic is of interest to scientists, many scientists will conduct experiments and make observations, whichthey will publish in scientific journals. Over time the evidence will mount in, for, or against the hypothesisbeing tested. If a hypothesis explains all the data and no data contradicts the hypothesis, the hypothesisbecomes a theory. A theory is supported by many observations and there are no major inconsistencies.A theory is also used to predict behavior. Although a theory can be overthrown if conflicting data isdiscovered, the longer a theory has been in existence the more data it probably has to back it up and theless likely it will be proven wrong. A theory is a model of reality that is simpler than the phenomenonitself.

The common usage of the word theory is very different from the scientific usage; e.g. I have a theory as towhy Joe likes Sue more than Kay. The word hypothesis would be more correct in most cases.

Scientific Models

Many scientists use models to understand and explain ideas. Models are representations of objects orsystems. Simpler than the real life system, models may be manipulated and adjusted far more easily.Models can help scientists to understand, analyze and make predictions about systems that would be

impossible without them.

Models are extremely useful but they have many limitations. Simple models often look at only a singlecharacteristic and not at the myriad conditions other aspects of a system. Since the scientists who constructa model often do not entirely understand the system they are modeling, the model may not accuratelyrepresent reality. Models are very difficult to test. One way to test a model is to use as its starting pointa time in the past and then have the model predict the present. A model that can successfully predict thepresent is more likely to be accurate when predicting the future.

Many models are created on computers because only computers can handle and manipulate such enormous

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amounts of data. For example, climate models are very useful for trying to determine what types of changeswe can expect as the composition of the atmosphere changes. A reasonably accurate climate model wouldbe impossible on anything other than the most powerful computers.

There are three types of models and each type is useful in certain ways.

Physical Models

Physical models are physical representations of whatever subject is being studied. These models may besimplified by leaving out certain real components, but will contain the important elements. Model carsand toy dinosaurs are examples of physical models. Drawings and maps are also physical models. Theyallow us to see and feel and move them, so that we can compare them to one another and illustrate certainfeatures.

We can use a drawing to model the layers of the Earth (Figure 8.13). This type of model is useful inunderstanding the composition of the Earth, the relative temperatures within the Earth, and the changingdensities of the Earth beneath the surface. Yet there are many differences between a cut-away model ofthe Earth and the real thing. First of all, the size is much different. It is difficult to understand the sizeof the Earth by looking at a simple drawing. You cant get a good idea of the movement of substancesbeneath the surface by looking at a drawing that does not move. The model is very useful but has itsshortcomings.

Figure 1.5: The Earths Center.

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Conceptual Models

A conceptual model is not a physical model, but rather a mental explanation that ties together many ideasto attempt to explain something. A conceptual model tries to combine knowledge and must incorporatenew knowledge that may change it as knowledge is acquired. The origin of the moon, for example, isexplained by some as a Mars sized planet that hit the Earth and formed a great cloud of debris and gas(Figure 1.6). This debris and gas eventually formed a single spherical body called the Moon. This is auseful model of an event that probably occurred billions of years ago. It incorporates many ideas aboutthe craters and volcanoes on the Moon, and the similarity of some elements on both the moon and theEarth. Not all data may fit this model, however, and there may be much information that we simply dontknow. Some people think that the Moon was initially an asteroid out in space which was captured in orbitby the gravity of the Earth. This may be a competing conceptual model which has its own arguments andweaknesses. As with physical models, all conceptual models have limitations.

Figure 1.6: A collision showing a meteor striking the Earth.

Mathematical Models

A third type of model is the mathematical model. These models are created through a great deal ofconsideration and analysis of data. A mathematical model is an equation or formula that takes manyfactors or variables into account. These models may help predict complex events like tornadoes andclimate change. In order to predict climate change, for example, a mathematical model may take intoaccount factors such as temperature readings, ice density, snow fall, and humidity. These data may beplugged into equations to give a prediction. As with other models, not all factors can be accounted for, sothat the mathematical model may not work perfectly. This may yield false alarms or prediction failures.No model is without its limitations.

Models are a useful tool in science. They allow us to efficiently demonstrate ideas and create hypotheses.They give us visual or conceptual manners for thinking about things. They allow us to make predictionsand conduct experiments without all of the difficulties of real-life objects. Could you imagine trying toexplain a plant cell by only using a real plant cell or trying to predict the next alignment of planets byonly looking at them? In general, models have limitations that should be taken into consideration beforeany prediction is believed or any conclusion seen as fact.

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Safety in Science

Accidents happen from time to time in everyday life. Since science involves an adventure into the unknown,it is natural that accidents can happen. Therefore, we must be careful and use proper equipment toprevent as many accidents as possible (Figure 1.7). We must also be sure to treat any injury or accidentappropriately.

Figure 1.7: Safety Symbols: A. Corrosive , B. Oxidizing Agent, C. Toxic, D. High Voltage.

Inside the Science Laboratory

If you work in the science lab, you may come across dangerous materials or situations. Sharp objects,

chemicals, heat, and electricity are all used at times in earth science laboratories. With proper protectionand precautions, almost all accidents can be prevented and suffering minimized (Figure 1.8). Below is alist of safety guidelines that you should follow when doing labs:

Follow directions at all times. Although working in the science lab can be fun, it is not a play area. Be sure to obey any safety

guidelines given in lab instructions or by the lab supervisor. Use only the quantities of materials directed. Check with your teacher before you do something

different than whats described on the lab procedure. Tie back long hair. Wear closed shoes with flat heels and shirts with no hanging sleeves, hoods, or

drawstrings.

Use gloves, goggles, or safety aprons when instructed to do so. Use extreme care with any sharp or pointed objects like scalpels, knives, or broken glass. Never eat or drink anything in the science lab, even if you brought it there yourself. Table tops and

counters could have dangerous substances on them. Keep your work area neat and clean. Be sure to properly clean and maintain materials like test

tubes and beakers. Leftover substances could interact with other substances in future experiments.A messy work area leaves more opportunities for spills and breakage.

Be careful when you reach. Flames or heat plates could be beneath your arms or long hair could getburned.

Use electrical appliances and burners as instructed. Know how to use an eye wash station, fire blanket, fire extinguisher, or first aid kit.

Alert the lab supervisor in the case that anything out of the ordinary occurs. An accident reportmay be required if someone is hurt and the lab supervisor must know if any materials are damagedor discarded.

Outside the Laboratory

Many earth science investigations are conducted outside of the science laboratory (Figure 1.9). Of course,the same precautions must be taken with lab-like materials but we must take additional considerations

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Figure 1.8: Safety Equipment in the Laboratory.

into mind. For any scientific endeavor outside or at home:

Be sure to wear appropriate clothing. Hiking into a canyon requires boots, long pants, and protectionfrom the sun, for example.

Bring sufficient supplies like food and water, even for a short trip. Dehydration can occur rapidly. Have appropriate first aid available. Be sure to let others know where you are going, what you will be doing, and when you will be

returning. Be sure to take a map with you if you dont know the area and you may leave a copy ofthe map with someone at home.

Be sure you have access to emergency services and some way to communicate. Keep in mind thatnot all places have coverage for cellular phones.

Finally, be sure that you are accompanied by a person familiar with the area to which you aretraveling or familiar with the type of investigation that you are going to do.

Review Questions

1. Write a list of five questions about the world around you that you find interesting.2. A scientist was studying the effects of oil contamination on ocean seaweed. He believed that oil runoff

from storm drains would keep seaweed from growing normally. He had two large aquarium tanks ofequal size. He monitored the dissolved oxygen in the water to keep it equal as well as the waterstemperature. He introduced some motor oil into one tank but not in the other. He then measured thegrowth of seaweed plants in each tank. In the tank with no oil, the average growth was 2.57cm. Theaverage growth of the seaweed in the tank with oil was 2.37cm. Based on this experiment, answerthe following questions:

(a) What was the question that the scientist started with?

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Figure 1.9: Outdoor Excursions.

(b) What was his hypothesis?(c) Identify the independent variable, the dependent variable, and the experimental control(s).(d) What did the data show?

3. Explain three types of scientific models. What is one benefit of each and one disadvantage of each?4. Identify or design five of your own safety symbols, based on your knowledge of safety procedures in

a science laboratory.5. Design your own experiment based on one of your questions from question 1 above. Include the

question, hypothesis, independent and dependent variables, and safety precautions. You may wantto work with your teacher or a group.

Vocabulary

conceptual model An abstract, mental representation of something using thoughts and ideas insteadof physical objects.

control Factors that are kept the same in an experiment, in order to focus just on the independent anddependent variables.

dependent variable The variable in an experiment that you are measuring as you change the indepen-dent variable. It depends on the independent variable.

hypothesis A good working explanation for a problem that can be tested.

independent variable The variable (or thing) in an experiment that is controlled and changed by theresearcher.

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mathematical model A set of mathematical equations and numbers that simulates a natural systembeing modeled.

physical model A representation of something using objects.

theory A hypothesis that has been repeatedly tested and proven to be true.

Points to Consider

What parts of the Earth do you think are most important and should be better studied? What type of model have you had experience with? What did you learn from it? What situations are both necessary and dangerous for scientists to study? What precautions do you

think they should use when they study them? If you could go anywhere, where would it be? What safety equipment or precautions would you take?

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